That’s according to former player turned pundit Ray Wilkins who’s slammed the Blues for selling the Serbian.

Matic swapped Stamford Bridge for Old Trafford in July and has impressed in a red shirt.

The 29-year-old was an important member of Antonio Conte’s title-winning team last season.

And Wilkins says Matic has improved Chelsea’s Premier League rivals and given Paul Pogba a new lease of life.

“It’s the worst [decision] I’ve ever seen, if I can say,” Wilkins said on Sky Sports.

“I cannot see that for the life of me.

Nemanja Matic and 12 other footballers who played for Jose Mourinho at more than one club

NEMANJA MATIC has signed for Manchester United - and he’s become the 13th footballer to play for Jose Mourinho at more than one club.

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13 footballers who have played for Jose Mourinho at more than one club

“Nemanja Matic joined Manchester United from Chelsea this summer”

“You’ve got a guy here who was so paramount to Chelsea along with Kante in the middle of the pitch, winning the championship with Chelsea the year before and all of a sudden you’ve sold him to one of or the biggest rival we have.

“I say we because I am a Chelsea supporter so I’m speaking from the heart when I speak.

“I just could not see that for the life of me, why would we let Nemanja go there?